1. Field of the Invention
This invention relates generally to new immunoregulatory chemical compounds, therapeutic compositions containing the same, and methods for preparation and use thereof, and particularly to immunoregulatory diketopiperazines.
2. Description of the Prior Art
U.S. application Ser. No. 20,157, filed Mar. 14, 1979, in the name of two of the present applicants discloses a class of peptides having ubiquitin-like activity, which peptides contain a GLN-LYS fragment alone or in combination with various numbers of sarcosine amino acid residues. The application discloses that these peptides have the same activity as the long-chain polypeptide ubiquitin disclosed in U.S. Pat. No. 4,002,602. This patent and application are incorporated herein by reference.
Reference is made to this patent and patent application for a detailed discussion of other prior art and the biological processes involved in the present invention.
The present invention provides diketopiperazines (cyclic dipeptides) which also have potent ubiquitin-like activity. Since ubiquitin itself and the peptides disclosed in the referenced patent application are all linear, it is most surprising that the subject diketopiperazines, which are cyclic, possess this same utility.